1. Field of the Invention
The present invention relates to improving the room heating capability of stoves, and free standing fireplaces, and more particularly to the provision of a blower driven air heater to be used in conjunction with a stove or freestanding fireplace.
2. Description of the Prior Art
Freestanding fireplaces and stoves, although commonly used in years past for heating a room or a house, have been generally replaced by more modern and efficient heating systems, such as a centrally located furnace used in conjunction with air ducts for distributing the warmed air to various locations in a house. Such furnaces are usually fueled by either stove oil or natural gas. However, due to the dimishing supply of the world's petroleum energy supply and the corresponding increase in the cost of home heating fuels caused thereby, alternative energy sources and home heating devices are being increasingly used. A renewed interest has developed in the conventional fireplace, the freestanding fireplace and stove, including the Franklin type stove, as alternative sources of primary or secondary heat for homes. Despite the fact that fireplaces and stoves are generally less efficient heating devices than more modern heating systems, because of the greatly increasing cost of stove oil and natural gas, the wood or coal burning fireplaces and stoves are becoming relatively more economical to operate.
In general, a freestanding fireplace or stove is more efficient than the conventional fireplace. The amount of heat transferred from the stove to the surrounding area by convection caused by the hot metal stove surfaces is greater than the combined transfer of heat from a fireplace to the adjacent air space due to radiation and convection. Still, compared to most modern heating systems, the stove is a relatively inefficient heating device. Much more air than is needed for efficient combustion of the fuel being used is withdrawn from the room and exhausted up the chimney along with the flue gases. To replace the warm air passing up the chimney, cold air is drawn into the room from the outside.
Numerous devices have been used in an attempt to increase the efficiency of stoves and fireplaces. Generally these devices have consisted of a heat exchanger located in or near the fire, a blower for forcing the room air through the heat exchanger and an outlet for directing the hot air warmed by the heat exchanger back into the room. One well-known expedient conforming to this general description is the hearth type heater having a heat exchanger constructed of an elongated hollow tube extending laterally across and positioned on the floor of a fireplace, with the fire being built above or directly on top of such tube. A blower for forcing room air through the tube is generally attached to one end of the tube heat exchanger and an outlet member for discharging the heated air into the air space being warmed is attached to the opposite end.
Another well-known device is the air heater used as, or in conjunction with, a fireplace grate. One common grate type heater includes a heat exchanger composed of a plurality of air tubes, either aligned with the grate bars, or themselves forming the grate bars. Normally an intake manifold is used to deliver cool room air from the blower to the individual tubes and an outlet manifold is used to collect the warmed air from the tubes and redirect such warm air into the surrounding air space.
Another known grate heating device includes a heat exchanger in the form of an enclosed box with an inlet and outlet opening at its front end for receiving cool air from a blower and for exhausting warmed air into the adjacent air space. The interior of the box includes baffles to deflect air flowing into the box from the blower to insure that such air circulates in an irregular path through the box so that such air remains in the box for a sufficient length of time to be adequately warmed prior to being discharged into the surrounding air space. The top wall of this box has elongated troughs or undulations forming a grate for holding the fuel being burned such as wood or coal.
Numerous drawbacks are common to grate and hearth type heaters. One disadvantage is that such heaters are constructed of a large number of individual parts and/or parts requiring expensive and complicated steps to manufacture, thus resulting in a rather expensive device in comparison to the cost of the stove itself. A second disadvantage of this type of structure is that the blower, providing air to the heat exchanger, is usually located in front of the grate, thereby causing noise from the blower to be emitted into the air space being heated. Another disadvantage is that the unsightly heat exchangers and blowers are visible from the front of the stove, greatly detracting from the appearance of freestanding fireplaces and antique stoves now being commonly used.
A type of air heater particularly adapted to be used in conjunction with stoves has been marketed by Therm-Air Industries, Inc. of Auburn, Washington and is disclosed in Design Patent Appln. Ser. No. 733,010 filed on Oct. 14, 1976, by Leroy A. Stull, of Auburn, Washington. This air heater includes a heat exchanger chamber of generally rectangular cross-section mounted to a stove back wall to extend into the firebox of such stove through an optional flue opening commonly provided in such stove back walls as an alternative location for the chimney pipe outlet. The heat exchanger is supported in such position by a separate mounting plate bolted to the exterior of the stove firebox at the location normally occupied by the optional flue cover plate which has been removed, such mounting plate includes bolt holes in registration with the mounting holes provided in the margin of the stove back wall opening. A blower, through the use of an adapter plate, is bolted to the mounting plate to deliver forced air to the heat exchanger through an inlet hole provided in such mounting plate, which inlet hole is in registration with an air inlet hole provided in the adjacent wall of the air heat exchanger. A plurality of hot air outlet tubes extend forward from the end wall of the heat exchanger opposite the mounting plate, to a location adjacent the front surface of the stove. An advantage of this type of air heater is that because the blower is mounted behind the stove, less noise is emitted from the blower into the air space being heated.
A disadvantage of the above-described stove air heater is that the exhaust tubes, which extend forward from the heat exchanger, are visible from the front side of the stove and thus detract from the appearance of the stove. This is especially true when such heaters are used in conjunction with antique styled Franklin type stoves. Another disadvantage is that because the hot air outlet tubes actually extend through the stove to discharge hot air foreward into the air space in front of the stove, this air heater cannot be operated with the front doors, commonly provided in such stoves, closed. Moreover, sparks and other burning material rising upwardly from the fire can be propelled into the room by the rapidly flowing air being discharged by the outlet tubes. A further disadvantage exists because the mounting holes located in the mounting plate must be in registration with corresponding holes provided in the stove side wall. Therefore, a different mounting plate must be provided with each stove having a different mounting hole pattern. The present invention relates to an improved version of this type of stove air heater.
Examples of the grate type air heaters are disclosed by the following U.S. Pat. Nos.: 3,942,509, granted Mar. 9, 1976, to Glen T. Sasser; and 4,008,706, granted Feb. 22, 1977, to John M. Buanno. An example of a hearth type heater is disclosed by U.S. Pat. No. 2,828,078, granted Mar. 25, 1958, to H. C. Snodgrass. These patents and the prior art that was cited and considered by the Patent Office before granting them, and which is listed on the patents, should be consulted for the purpose of properly evaluating the subject invention and putting it into proper perspective.